1. Field of the Invention
The present invention relates to an electric stapler provided with a driver unit including a driver for striking out a staple to bind sheets of paper and a clincher unit including a clincher for bending the staple struck out and penetrated through the sheets of paper.
2. Related Art
Patent reference 1 and Patent Reference 2 disclose vertically separated type saddle stitching staplers in which centers of paper bundles are bound. In an operation using these staplers, a central portion of the sheets of paper are bent, the portion are thereafter inserted into a binding space between a driver unit and a clincher unit, then the sheets of paper are bound. Since the bent portions of the centers of the sheets of paper are stacked in a manner that the centers direct upward, it is general to dispose the driver unit in an upper side and the clincher unit in a lower side. However, in this structure, since the stacking height of the bent portions tends to be high, in order to prevent the high bent portions from interfering, it is necessary to spread the binding space intervening between the two units. Especially, in order to be able to bind about fifty sheets of paper, the binding space must be spread considerably widely.
Also, when binding the sheets of paper, the driver unit or clincher unit is projected toward its partner so that the binding space is thereby narrowed; the paper bundle is clamped; the driver is driven to penetrate the staple through the sheets of paper; and then the sheets of paper are clinched by the clincher unit. Normally, since bent sheets of paper are stacked and set on the clincher unit, a clamp mechanism is disposed on the driver unit side and the driver unit is moved down to clamp the bundle of the sheets of paper. In this case, in a structure in which the whole of the driver unit is moved down using a separate mechanism, an apparatus having such structure becomes large in size. In view of this, there is employed a clamp structure in which, of the driver unit, a staple storage portion and a head portion including the periphery of the driver are separated from a drive portion for driving the driver and the like, and the staple storage portion and head portion are moved down to thereby clamp the sheets of paper (see the patent reference 1). The reason why such structure is employed is that, it is believed that the staple storage portion and head portion cannot be separated from each other, since a leading staple is fed out to the strike-out portion from the staple storage portion in which a large number of staples are stored and the thus fed-out leading staple is then struck out using the driver.
Here, in the case that the binding space is set wide, the range of a vertical movement of the head portion of the driver unit also widens. Since the movable portion of the electric stapler, which includes the staple storage portion and head portion, includes such staple storage portion as contains therein about 5000 to 7000 pieces of connected staples, the movable portion is heavy in weight. Thus, the load of a current necessary for driving the heavy movable portion greatly in the vertical direction is inevitably large and noises generated when the electric stapler is in operation also become loud accordingly.
Also, when the considerable heavy movable portion moves up and down suddenly, the connected portions of the connected staples within the staple storage portion can be separated from each other due to vibrations caused by the sudden vertical movement of the movable portion, and a feed pawl for supplying the connected staples to the strike-out portion can be caused to come off due to the bouncing movements of the connected staples, thereby raising a possibility that poor staple feed can occur.
Further, as the staples are consumed or new staples are supplied, the number of staples contained within the staple storage portion decreases or increases, whereby the weight of the staple storage portion decreases or increases. Therefore, when the staple storage portion and head portion move integrally, the center of gravity of the whole of the moving portion varies accordingly, whereby the binding core position is made easy to change. In addition to this, when the stroke of the moving portion in the vertical movement thereof is large and also the staple storage portion bounces, the binding positions of the staples are caused to vary, thereby raising a possibility that the binding of the papers by the staples can be unstable.
Further, Patent Reference 3 is a reference disclosing a stapler in which a straight staple is formed into a U-shape, and then the formed U-shape staple is driven into sheets of paper.
[Patent Reference 1] JP-U-06-063342
[Patent Reference 2] JP-A-2005-314029
[Patent Reference 3] US 2006/0273133